1. Field of the Invention
The present invention relates to a display device including an electrochromic layer.
2. Description of the Related Art
Display devices utilizing electrochromism in which color changes through an electrochemical oxidation-reduction reaction have been known. In such display devices utilizing electrochromism, long-duration display at low voltage, long life, and the like can be expected.
For example, Japanese Unexamined Patent Application Publication No. 1-277825 (Patent Document 1) discloses an invention of an electrochromic light controlling plate in which counter electrodes (resistive films) and coloring films are disposed on inner surfaces of substrates facing each other and a space between the coloring films is filled with an electrolyte.
In Patent Document 1, a first electrode drawn portion and a second electrode drawn portion are further disposed at both ends of each of the counter electrodes. After a coloring voltage is applied to the first electrode drawn portion until a colored region of the coloring film reaches a predetermined region, the application of a decolorizing voltage to the second electrode drawn portion and the application of a coloring voltage to the first electrode drawn portion are alternately performed in a repeated manner. Thus, the colored region can be retained in only part of the coloring film.
However, in the invention disclosed in Patent Document 1, after the colored region of the coloring film has reached a predetermined region, the application of a decolorizing voltage to the second electrode drawn portion and the application of a coloring voltage to the first electrode drawn portion are alternately performed in a repeated manner. Therefore, the colored region is easily fluctuated, resulting in unstable displaying. Furthermore, a relatively large screen causes no problem, but, in a small screen, it is believed to be quite difficult to alternately time-control the application of a coloring voltage and the application of a decolorizing voltage so that only part of the colored region is retained.
In an invention disclosed in Japanese Unexamined Patent Application Publication No. 2010-66585 (Patent Document 2), the display speed in a display region is changed by changing the distance between counter electrodes. However, it is believed to be quite difficult to control the distance between the counter electrodes so that the display speed has an optimum difference. In addition, various different displays cannot be achieved in the configuration disclosed in Patent Document 2. The invention disclosed in Patent Document 2 can be applied to only a display form in which coloration gradually proceeds. That is, it is impossible to retain only part of the colored region. For example, the display form shown in FIG. 2(b) of Patent Document 2 cannot be retained.